According to The Australian Financial Review today, first it was Japan Post with a knockout $6.5 billion for out-of-favour Toll Holdings. And now a Japanese bidder, Nippon Life, is knocking on the door at National Australia Bank's unloved life insurance unit talking numbers that would have surprised most shareholders and analysts.With bonds at zero, Japanese investors are showing they're happy to accept single digit returns on investment and a considerable appetite for Australian companies.And hedge funds and bankers are starting to wonder where the bidders will show up next.Japanese companies have shown a liking for financial services. And it was only five years ago, Japan's Dai-Ichi Life snapped up another of Australia's biggest life insurers, TAL, in a $1.2 billion deal. Then there was Nikko Asset Management, which purchased fund manager Tyndall Investments.The NAB life approach from Nippon appears timely, with profits across the sector suffering from low investment yields. With investment income being a big driver of profits, the Japanese insurer would be itching to boost its balance sheet with an acquisition that promised some form of growth.The mooted offer from Nippon is above what the broker thought would be NAB Life's realisable value last year of $800 million.Investment bank JPMorgan is advising NAB on the potential deal, with Nippon Life believed to have tabled a price north of $2.5 billion.